Power subsystem for Spacebus and Arabsat
ESA's technology R&D activities have four primary objectives:
All of the Technology Programme's efforts are focused on these goals, with ESTEC playing a vital role in coordinating the preparation and management of the many activities. ESTEC also plays a 'federative' role not only between the different ESA Programme Directorates, but also with European industry and the national space agencies.
The Basic Technology Research Programme (TRP) covers all of the common domains of technology applicable to medium-and long-term missions, and advances technological research to the point of demonstrated feasibility.
The Preparatory and Support Technology Programme (STP) elements cover the major programme areas and are directed towards near-to medium-term needs, advancing technology to the point of demonstrating flight suitability.
The General Support Technology Programme (GSTP) is an optional supporting technology programme that was initiated in 1993 primarily to ensure continuity in critical development areas. It is product-oriented. All ESA Member States currently participate in the GSTP, together with Canada. The collaborative activities undertaken are providing better harmonisation with minimum use of resources. GSTP-2 (second GSTP phase starting in early 1996) will encourage industry to participate in the funding of the various activities.
The In-Orbit Technology Demonstration Programme (TDP) provides in-orbit demonstration opportunities for European technology which cannot be properly tested and qualified on the ground prior to its incorporation into the hardware stages of new space projects.
The cross-fertilisation between projects and programmes provided by the above technology programmes has created a unique centre of competence at ESTEC, leading to continuous progress and improvements in performance, better coordination between all parties, and improved adaptability to changing environments and policies. An important aspect of this synergy is that it avoids unnecessary duplication of effort and channels existing knowhow into the successful conduct of ESA's projects. Technology R&D activities (TRP, GSTP, TDP, etc.) currently represent less than 4% of the ESA budget. Nevertheless, there have been many noteworthy achievements in recent years, a selection of which are summarised below, in association eith the Technology Programme's current activities and future objectives. The various challenges that ESA was confronted with in the dirrefent sectors are highlighted, together with the areas where continuity of effort has led to the qualification and commercialisation of components, systems, or equipment for national, European and World markets.
A central Technology Advisory Committee (CTAC) has been set up to strengthen ESA's technology programmes still further. This Committee, consisting of leading authorities in both the scientific and technical fields, will attempt to identify strategic areas of space technology where efforts should be undertaken on a European scale, and the consistency of ESA's efforts with respect to other national or European programmes.
The need was for an advanced power subsystem for future generations of medium-to high-power telecommunications satellites using a regulated power bus, with power levels of up to 5 kW. The objective was ti develop a system that could be baselined for the Spacebus-3000 series of spacecraft under consideration by Aérospatiale (F) at that time.
This development effort was so successful that Aérospatiale, who were in the process of bidding for the Arabsat project, asked ESA to re-direct the engineering- and flight-model activities specifically towards this programme. As a result, ETCA (B) have firm orders for: two systems for Arabsat, two for Thaisat, and two for ongoing proposals. This design also forms the baseline for Aérospatiale's bid for Eutelsat-3 (three satellites, and an option for a further four).
Power subsystem for Spacebus and Arabsat
The need was for high- performance solar cells for spacecraft operating at very large distances from the Sun, where the solar-radiation's intensity is only about 10% of that near Earth and the equilibrium temperatures of solar arrays are reduced to about 100 deg C. Previous deep-space probes have had to rely on Radioisotope Thermoelectric Generators (RTGs) using radioactive power sources. ESA decided to develop an alternative power source for such missions based on very-high-efficiency solar cells.
As a result, a 25% efficiency figure has been achieved under low-intensity/low-temperature (LILT) conditions using 6 x 4 cm 2 silicon cells. This is the highest efficiency ever achieved with such cells without special optical concentration. These cells can power deep-space missions like Rosetta out to the distance of Jupiter's orbit from the Sun, using array technologies already available in Europe.
Features of a LILT silicon solar cell
Microwave system performance depends strongly on the capabilities of the key electronic components. For the past 20 years, the microwave active-component market has been dominated by just a few non-European suppliers, with consequent high cost, low technical visibility and, more recently, operational failures. An ambitious technology programme was therefore started a few years ago aimed not only at achieving European autonomy, but also developing very high performance devices at competitive prices.
The results have been extremely encouraging, leading to the first ever formally space-qualified High Electron Mobility Transistors in the World, which will be used extensively on Europe's Artemis and Envisat spacecraft.
In the area of power microwave technology, Europe is currently fully dependent on Asian suppliers. Here again, a co-funded DARA/ESA programme has demonstrated that the requisite technology is not only available in Europe, but can provide better performance at lower cost.
Several national projects have already selected components developed under these activities.
Significant commercial success has been achieved with 50-80 K and 80 K coolers. Matra Marconi Space (UK) has already sold more than 20 units, and has orders for many more, including customers in many non-European countries.
Development of a second-generation 50-80 K cooler based on pulse-tube technology is now in progress, which will allow Europe to remain a World leader in the cooler field. Consolidation of cooler technology for very-low-temperature applications, e.g. 20 K, 4 K and below 1 K, is also in process. Many of the associated activities relate to the ESA Scientific Programme's Cornerstone mission 'First'.
Future developments are geared to maintaining European leadership in cooler technology and meeting - at minimum spacecraft system-level cost - the ever-increasing cooling demands from the user community.
The 20K cryocooler
The Technology Programme has concentrated on development of those units and components specifically needed for space missions, for example space-qualified microprocessors, solid-state recorders, etc. The success of this effort is well-demonstrated by the radiation-hard,2 MIPs microprocessor developed by GPS (UK), which is now being used in all ESA programmes, as well as by the US commercial space market. It represents a technology spin-off of considerable value, technically as well as financially.
Another product of the programme lies in the use of 2 Gbit solid-state recorders on ESA's Soho and Cluster missions, and the planned use of 30 Gbit-plus recorders on many of the Agency's future missions.
The rapidly increasing demands and evolution in technology call for continued development effort, and two further significant activities have therefore been started, namely development of a 10 MIPs- plus 32-bit SPARC microprocessor and the ADSP 21020 digital signal processor in radiation-hard technology (MHS/F). The latter activity has been undertaken in coordination with the European Union's Esprit/Framework Open Microprocessor Systems Initiative (OMI) programme.
The increasing use of software in space systems makes the production of highly reliable software systems at lower cost a key issue. Initial work on automatic code generation has shown that an order of magnitude improvement in software reliability and productivity can be achieved by such methods.
The 2 MIPs microprocessor
Technology developments in this area have always been undertaken in the context of their direct application in one or more programmes, the On-Board Processor (OBP) Switch and Rubidium Ultra-Stable Oscillator (RUSO) being two good examples. The OBP Switch is used on satellites with multiple spot beams, regeneration and switching on board. Developed by the Observatoire Cantonal de Neuchatel under the TDP-2 programme, the RUSO combines exceptional frequency stability with low mass, power consumption and volume. Flight models will be delivered in December 1995 for a demonstration flight on the Russian Radioastron-1 spacecraft. Applications of this technology include metrology, telecommunications and navigation, and in particular the future Global Navigation Satellite System GNSS-2.
Planned technology activities for the coming years are focussed on two objectives:
To meet the enhanced telecommunications capabilities needed by deep-space missions, design of a deep-space transponder operating at X- or Ka-band (8 or 30 GHz) has been initiated in the framework of the TRP. Development of a fully-integrated breadboard is proposed in the framework of the GSTP-2 Programme.
One example of generic hardware is the Satellite Navigator and Attitude Determinator (SNAD), a navigation receiver that, in addition to accurate satellite orbit information, will offer a very precise and far less expensive means of determining a spacecraft's attitude.
T-stage multichip module for RF systems
ESA's earlier R&D efforts in the area of submillimetre heterodyne radiometry have led to technological readiness for a new class of spaceborne sensors which can measure key molecular species both in the Earth's atmosphere and in outer space. Such sensors have the sensitivity and spectral resolution needed to detect those minor constituents affecting our climate, or even those species that carry the signature of the primordial Universe. Sensors are now available with demonstrated performance for use in advanced Earth-observation and space-astronomy missions.
Superconducting radiometric receiver unit
Field-Emission Electric Propulsion (FEEP) thrusters originally developed at ESTEC are being further developed for application onboard spacecraft that require high-precision pointing and low-acceleration features (scientific and Earth-observation missions). There is now increasing interest in micro/nano-technologies for space applications, and FEEP also qualifies for this type of use.
FEEP thruster
Wave interaction and propagation
A new modular software package
(called 'Dapper') has been developed by Siemens (A) for use in the standardised processing and
analysis of data originating from different microwave propagation experiments. The package was
sub-licensed to all members of the Olympus satellite's Propagation Experimenter Group, thereby
contributing to the success of the OPEX campaign.
Antennas
TRP activities have led to the pre-qualification of many antenna designs, allowing them
to be utilised in orbit with short lead times, for both ESA's own and commercial missions.. These
initiatives have therefore allowed European companies to compete successfully in the international
market place by offering appropriate antenna subsystems at competitive prices and with the
requisite short delivery times.
Key examples are:
Future developments are directed towards even more competitive, lightweight, low-distortion reflection technology and more advanced array technologies, to meet both telecommunications and Earth-observation mission needs.
C-band dual circularly polarised antenna feed
In addition to its many applications in the space sector, other industries have also recognised the potential of the ESA-developed Test Data Analysis System (TDAS/EMC) as a unique tool providing a more cost-effective approach to the EMC engineering of complex electronic systems. Consequently, thirty-one licences have already been granted.
Far Infrared and Submillimetre Space Telescope (First) mission is an astronomical observatory for spectroscopy, imaging and photometry, operating in the 0.1 to 1.0 mm spectral wavelength range. It requires a 3 m-diameter antenna reflector with a surface shape accuracy of better than 5 microns at an operating temperature of 110 K.
A 1.1 m prototype reflector developed within the TRP has demonstrated the feasibility of the reflector's accuracy, thermal-stability and mass requirements. It applies special low-temperature- curing CFRP in the reflector face sheets and core. This technology, developed at Daimler Benz Aerospace, outperforms its worldwide competitors and has therefore been proposed as the baseline technology for First in the industrial offers.
Prototype 1.1m antenna reflector for First
A breakthrough in terms of minimising on-board disturbance has been achieved with the feasibility demonstration of a noise- attenuated magnetic-bearing momentum wheel. By incorporating special electronic filters into the wheel's active magnetic suspension system, the vibrational disturbances transmitted to the spacecraft are 100 - 1000 times lower than from conventional wheels.
There is strong interest in this development from numerous European and American satellite manufacturers, including Matra Marconi Space (MMS), Intelsat, Martin Marietta, Loral and Hughes. The device has already been baselined by MMS for use on the French technology-demonstration satellite Stentor.
Magnetic-bearing momentum wheel
Impact damage on solar panels
Several development efforts have been pursued to enable payload operations and servicing by a small robotic manipulator inside the Space Station' pressurised laboratories, both for concept development (EMATS) and to provide building blocks such as the Space Automation Robotics Controller (SPARCO). The latter is being further elaborated as the flight controller for the JERICO (Joint European Robotic Interactive Calibrated Operation) in-orbit experiment. It may also be used in a servicing facility for exposure platforms (EXPRESS, MEF) on the Space Station.
Novel work has been done under the magnetic-gearing contract with the goal of achieving magnetic rather than mechanical reduction of motor speed, for greater accuracy and reliability.
The Sun has important and sometimes dramatic effects on the near-Earth environment. It triggers geomagnetic storms during which the radiation and plasma environments become severe and possibly space-mission-threatening. Spacecraft are also threatened by bombardment from high-velocity particles in the form of natural meteoroids and debris left in orbit by man's space activities.
ESA provides help to European space industry in evaluating the effects of these environments on future space missions. Through its research programmes, it collaborates with industry in analysing data on the space environment or spacecraft experiences with environmental effects. It thereby develops standard environment models and assessment methods to be used in building satellites, so that mission goals will not be compromised, over-design of satellites can be avoided, and cost and risk can be minimised. The fact that industry is armed with good information and tools for designing its products to survive the space environment makes European spacecraft that much more competitive.
The risks of space flight originate primarily from the hazardous characteristics of, and failures in, the design and operation of complex space systems. ESTEC's Product Assurance and Safety Department has developed an advanced and internationally applied risk-assessment approach, which allows the systematic identification and minimisation of these uncertainties. Future applications will be supported by the RAMS Expert System (ERES) presently under development, which will constitute the second generation of the current ESA risk- analysis software (RISAN).
Study of shape deformations in large spacecraft structures, such as the antennas of communications satellites and large space reflectors, is essential to the successful design of any space system. Consequently, there is great interest in accurately characterising the performance of such structures under operational conditions.
ESTEC's Testing Division, in conjunction with Rollei (D), has developed a photogrammetry system that can accurately monitor the structural deformation of these large objects due to Sun-induced thermal stress, under simulated space conditions. It relies on a vacuum-proof camera-canister system able to work with high precision under the harsh environmental conditions present in ESTEC's Large Space Simulator (LSS) during testing operations. The system achieves accuracies of 30 microns for objects 3 m in diameter.
Artemis spacecraft antenna reflector during measurements in the ESTEC LSS
This module is designed to monitor the gas composition in life- support loops for biological experiments. The data can be used for gas-composition control, metabolic monitoring, and to provide housekeeping data for the investigator. The novelty of this instrument lies in the combination of all the necessary components in one common block.
In addition to its application potential for all biological facilities and experiments associated with life- support in space, it has good commercial market potential for monitoring gas composition in greenhouses and controlled-atmosphere storage areas for fruits like apples and bananas.
Gas monitoring module
RadFETs, originally developed under ESA contract to measure radiation intensity in space, are now finding applications beyond the Agency's programmes. These miniature solid-state sensors, manufactured at NMRC in Cork (Irl), have been selected by the Japanese Space Agency (NASDA) for potential use in its ADEOS and JEM projects.
RadFET devices have also been flown on the British STRV satellite, and will be used in future Defence Research Agency projects. The application of RadFETs to radioactive-waste management is also being studied in the USA, and RadFET devices are undergoing clinical trials at two UK hospitals in connection with cancer treatment.
RadFET
Regular information about the many new space technologies being developed in Europe is provided in the newsletter 'Preparing for the Future', published by ESA Publications Division and available in both paper copy, and via the Internet:
http://esapub.esrin.esa.it/esapub.html
ESA has set up a Technology Transfer Programme to stimulate the wider use of technology developed within the European space research community. The goal of this programme is to promote the transfer of innovative technology from space to non- space applications. A central medium for promoting transfers of space technology is the annual Technology Catalogue produced by Spacelink Europe on behalf of ESA (TEST).
The ESA Programmes (BR-114).